This invention relates to receivers of radio frequency signals, and, in particular, to a transistor amplifier and mixer input stage for a receiver that can be implemented in integrated circuit technology.
The dynamics of a receiver's input stage, i.e., the difference between maximum and minimum input signal levels that can be accepted without introducing appreciable distortion, are limited in its lower signal level range by input stage sensitivity and in its upper range by the deviation from the linearity of the transfer characteristic of the input stage.
A number of devices are known to control or modify the input stage circuit in a simple way in order to expand upwards the input signal dynamics. In particular, one device is described in the Italian Patent Application No. 23984 A/81, filed on Sept. 16, 1981 and assigned to the assignee of the instant U.S. patent application which will be referred to later in this description. This device, while fully satisfying the above-mentioned goal, has the disadvantage of causing transients thereby producing nonlinearity in the input stage function and discontinuity in the gain. These phenomena can cause a distortion of the signal and can lower the signal output level. Furthermore, the device does not work properly with power supplies under 2 Volts.